crank replacement, Jackson

Good afternoon - the crank assembly in one of my house windows has gone bad. It no longer cranks the window inward. This is a left-side opening window, with part number R30842 stamped on one of the arms. The housing has worn away and cracked, which I assume is part of the problem. The crank arm will not stay in place, and wants to pop out.

Your assistance is appreciated. -Tom